We endorse all of the comments and observations made in the Preface to the First Edition of this book. Over the last 8 years, considerable progress has been made in opening soil processes up for scientific inquiry, indeed, viewing soils “through a ped darkly” (Coleman, 1985) and getting away from the simplistic approaches of the “black box” that prevailed in much of the 20th century. In the midst of the wonder and awe surrounding the pictures that have been transmitted across 100 million miles to Earth during 2004 from the two Mars rovers, it is important to point out a basic fallacy in the discussions over the findings on the surface of Mars. The engineers and physical scientists in charge of the study persist in calling the Mars surface material “soil.” As we note many times in our book, biology is the leading characteristic of soil. Organisms are one of the five major soilforming factors, and life itself characterizes a true soil. Anything found on the surface of Mars—barring totally unexpected news to the contrary—is no doubt complex and interesting, but it is essentially weathered parent material, not soil. Arthur C. Clarke came closer with the title of his science fiction novel Sands of Mars. On the biological side of soil studies, much progress has been made recently in elucidating not only biotic function, especially in the case of bacteria and fungi, but also the identity of which species is performing what process. We focus primarily on the biological aspects, and devote a smaller proportion of our total coverage to soil physics and chemistry, largely because they are discussed extensively in recent treatises by Hillel (1997) and Brady and Weil (2000). As a reflection of these new developments, we have singled out Soil Biodiversity and Linkages to Soil Processes for coverage in its own chapter (Chapter 7) to identify and emphasize one of the areas of burgeoning research and conservation interest. Also included is a final chapter (Chapter 9) on laboratory and field exercises that have proven useful in our course in Soil Ecology at the University of Georgia. We hope they will be helpful to faculty and students who use this book. We invite our readers to become “Earth rovers,” and participate in the wonder and excitement of studying the ecology of soils, a marvelously complex milieu. We hope that this textbook, along with other recent ones, such as the extensive compendium of Lavelle and Spain (2001), will provide the interested scientist with some of the background necessary to work in this often difficult but always fascinating field of research. Two colleagues who were instrumental in critiquing our first edition, Eugene P. Odum and Edward T. Elliott, are now deceased, but their influence is still felt by the soil ecology community and by us. A new generation of students and postdoctoral fellows from the University of Georgia and other universities have contributed ideas and inspiration to this effort, including: Sina Adl, Mike Beare, Heleen Bossuyt, George Brown, Weixin Cheng, Charles Chiu, Greg Eckert, Christien Ettema, Shenglei Fu, Jan Garrett, Randi Hansen, Liam Heneghan, Nat Holland, Coeli Hoover, Shuijin Hu, John Johnston, Keith Kisselle, Sharon Lachnicht, Karen Lamoncha, Stephanie Madson, Rob Parmelee, Mitchell PavaoZuckerman, Kitti Reynolds, Chuck Rhoades, Breana Simmons, Guanglong Tian, Petra van Vliet, Thaïs Winsome, Christina Wright, David Wright, Qiangli Zhang, and our soil ecology colleagues at the University of Georgia, Colorado State University, Oregon State University, University College Dublin, and at many LTER sites around the world. Any errors are of course ours, and we would appreciate comments from readers pointing them out.